1. Field of the Invention
The present invention relates to antenna selection for a device in a wireless communication system, and in particular to antenna selection techniques for fast diversity.
2. Related Art
FIG. 1 illustrates an exemplary wireless communication system 100 including two transceivers 101 and 102. Transceiver 101 includes a transmitter 101A, a receiver 101B, an antenna selection block 101C, and antennas 101D. Similarly, transceiver 102 includes a transmitter 102A, a receiver 102B, an antenna selection block 102C, and antennas 102D. In one embodiment of wireless communication system 100, one antenna of antennas 101D and one antenna of antennas 102D can be selected by antenna selection blocks 101C and 102C, respectively, for use by transceivers 101 and 102. In another embodiment of wireless communication system 100, multiple antennas of antennas 101D and multiple antennas of antennas 102D can be selected by antenna selection blocks 101C and 102C, respectively, for beamforming by transceivers 101 and 102.
In many environments, a transmitted signal between transceivers 101 and 102 can be reflected along multiple paths before being received (i.e. have multipath conditions). As a result, the transmitted signal can experience phase shifts, time delays, attenuations, and distortions, all of which should be corrected to be accurately decoded. Antennas 101D and 102D have different physical locations and therefore have different multipath conditions.
Antenna diversity is a known technique for improving the quality and reliability of communication between transceivers 101 and 102 by selecting antennas that successfully mitigate multipath. For example, if a first antenna of antennas 102D is experiencing significant multipath fading, it is probable that a second antenna of antennas 102D is experiencing less multipath fading. Selecting the second antenna rather than the first antenna of antennas 102D might improve system performance.
In wireless communication system 100, antenna selection blocks 101C and 102C can determine which antennas will be used for receiving packets. Antenna selection blocks 101C and 102C can be software driven (slow diversity) or hardware driven (fast diversity). Conventionally, slow diversity makes decisions by considering the long-term PER (packet error rate) history of each receive antenna. In contrast, fast diversity relies on the instantaneous receive power, e.g. the received signal strength indicator (RSSI).
Although fast diversity can track the instantaneous channel condition more quickly, both measurements and computer simulation results indicate RSSI may not be an accurate metric, especially when the power difference between receive antennas is not significant. Therefore, a need arises for a technique providing accurate fast diversity.